This invention relates generally to illumination devices, and, more particularly, to illumination devices of the type used by physicians and surgeons to provide a high intensity light source with an area of illumination controllable without use of the hands, usually by head movement.
One illumination device of this general type consists of a headband supporting a conventional incandescent lamp and a reflector. A device of more recent development consists of a headband which utilizes light-conducting glass optical fibers and a remote light source to provide illumination. In this latter device, a bundle of glass optical fibers is mounted with a lens on the headband and projects light in front of the wearer.
Illumination devices of both these types suffer from the principle disadvantage that they are much too heavy and cumbersome to wear for prolonged periods. Glass optical fibers are also relatively fragile and inflexible, and typically utilize a relatively heavy sheathing material. Attempts to replace the heavy glass fiber and sheathing combination with lightweight, polymer optical fibers, have hitherto been largely unsuccessful, except at very low light intensities. Connection of polymer optical fibers to a high-intensity light source generally results in melting of the fibers when the luminous flux delivered by the light source exceeds approximately 200 lumens. Ideally, light sources delivering over 1,000 lumens are preferred for surgical applications.
Although the use of glass optical fibers permits the transmission of light at a relatively high luminous flux level, glass fibers suffer from the aforementioned disadvantages of relatively high weight, fragility, and inflexibility. These characteristics unduly restrict the head movement of the wearer, and the fibers may even break as a result of repeated head movements.
Moreover, because of the relatively large weight of illumination devices of both the glass fiber-optic type and the conventional incandescent type, such devices usually provide only a single, relatively narrow area of illumination. Such narrow field illumination from a single light source makes it difficult to cast light into a work area without causing shadows.
Yet another disadvantage of the aforementioned illumination devices is that a wearer who requires prescription eyeglasses must wear, in addition to his eyeglasses, a cumbersome head-mounted illumination device to which he is not easily accustomed. Furthermore, so that the light is emitted at eye level, such illumination devices are often positioned to the center and in front of the wearer's eyeglasses, and thereby present a risk of partially obstructing the wearer's vision.
It will be apparent from the foregoing that there is a significant need, particularly felt in the medical profession, for a lightweight illumination device which may be worn on the head, but which produces light at luminous flux levels well in excess of 200 lumens, preferably from more than one point source, to minimize shadows, and preferably using an arrangement which does not necessitate the wearing of separate eyeglasses. The present invention satisfies this need.